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ABSTRACT: BACKGROUND AND PURPOSE: Thermostabilisation by mutagenesis is one method which has facilitated the determination of high resolution structures of the adenosine A2A receptor (A2A R). Sets of mutations were identified which both thermostabilised the receptor and resulted in preferential agonist (Rag23 mutant) or antagonist (Rant5 and Rant21) binding forms as assessed by radioligand binding analysis. While the ligand binding profiles of these mutants are known the effects these mutations have on receptor activation and downstream signaling are less well characterised. EXPERIMENTAL APPROACH: Here we have investigated the effects of the thermostabilising mutations on receptor activation using a yeast cell growth assay. The assay employs an engineered Saccharomyces cerevisiae, MMY24, which couples receptor activation to cell growth. KEY RESULTS: Analysis of the receptor activation profile revealed that the WT A2A R had considerable constitutive activity. In contrast the Rag23, Rant5 and Rant21 thermostabilised mutants all exhibited no constitutive activity. While the preferentially antagonist binding mutants Rant5 and Rant21 showed a complete lack of agonist-induced activity, the Rag23 mutant showed high levels of agonist-induced receptor activity. Further analysis using a mutant intermediate between Rag23 and WT indicated that the loss of constitutive activity observed in the agonist responsive mutants was not due to reduced G-protein coupling. CONCLUSIONS AND IMPLICATIONS: The loss of constitutive activity may be an important feature of these thermostabilised GPCRs. In addition, the constitutively active and agonist-induced active conformations of the A2A R are distinct.
British Journal of Pharmacology 03/2013; · 4.41 Impact Factor
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ABSTRACT: Soap opera: Fluorinated amphiphile F4-MNG confers greater stability on Rhodobacter capsulatus superassembly relative to conventional detergents and nonfluorinated MNGs. Such amphiphiles are attractive as tools for membrane science because of their ease of preparation and structure variation.
ChemBioChem 03/2013; 14(4):452-5. · 3.94 Impact Factor
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Pil Seok Chae,
Rohini R Rana,
Kamil Gotfryd,
Søren G F Rasmussen,
Andrew C Kruse,
Kyung Ho Cho,
Stefano Capaldi,
Emil Carlsson,
Brian Kobilka,
Claus J Loland,
Ulrik Gether,
Surajit Banerjee, Bernadette Byrne,
John K Lee,
Samuel H Gellman
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ABSTRACT: The development of a new class of surfactants for membrane protein manipulation, "GNG amphiphiles", is reported. These amphiphiles display promising behavior for membrane proteins, as demonstrated recently by the high resolution structure of a sodium-pumping pyrophosphatase reported by Kellosalo et al. (Science, 2012, 337, 473).
Chemical Communications 11/2012; · 6.17 Impact Factor
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ABSTRACT: The innate immune system provides the first line of host defence against invading pathogens. Key to upregulation of the innate immune response are Toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns (PAMPs) and trigger a signaling pathway culminating in the production of inflammatory mediators. Central to this TLR signaling pathway are heterotypic protein-protein interactions mediated through Toll/interleukin-1 receptor (TIR) domains found in both the cytoplasmic regions of TLRs and adaptor proteins. Pathogenic bacteria have developed a range of ingenuous strategies to evade the host immune mechanisms. Recent work has identified a potentially novel evasion mechanism involving bacterial TIR domain proteins. Such domains have been identified in a wide range of pathogenic bacteria, and there is evidence to suggest that they interfere directly with the TLR signaling pathway and thus inhibit the activation of NF-κB. The individual TIR domains from the pathogenic bacteria Salmonella enterica serovar Enteritidis, Brucella sp, uropathogenic E. coli and Yersinia pestis have been analyzed in detail. The individual bacterial TIR domains from these pathogenic bacteria seem to differ in their modes of action and their roles in virulence. Here, we review the current state of knowledge on the possible roles and mechanisms of action of the bacterial TIR domains.
Medical Microbiology and Immunology 07/2012; · 3.83 Impact Factor
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Pil Seok Chae,
Søren G F Rasmussen,
Rohini R Rana,
Kamil Gotfryd,
Andrew C Kruse,
Aashish Manglik,
Kyung Ho Cho,
Shailika Nurva,
Ulrik Gether,
Lan Guan,
Claus J Loland, Bernadette Byrne,
Brian K Kobilka,
Samuel H Gellman
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ABSTRACT: Non-traditional amphiphiles: Conferring aqueous solubility on membrane proteins generally requires the use of a detergent or other amphiphilic agent. A new class of amphiphiles was synthesized, based on steroidal lipophilic groups, and evaluated with several membrane proteins. The results show that the new amphiphile, "glyco-diosgenin" (GDN; see figure), confers enhanced stability to a variety of membrane proteins in solution relative to popular conventional detergents, such as dodecylmaltoside (DDM).
Chemistry 06/2012; 18(31):9485-90. · 5.93 Impact Factor
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ABSTRACT: Abstract Despite detailed genetic and mutagenic analysis and a recent high-resolution structure of a bacterial member of the nucleobase-ascorbate transporter (NAT) family, understanding of the mechanism of action of eukaryotic NATs is limited. Preliminary studies successfully expressed and purified wild-type UapA to high homogeneity; however, the protein was extremely unstable, degrading almost completely after 48 h at 4°C. In an attempt to increase UapA stability we generated a number of single point mutants (E356D, E356Q, N409A, N409D, Q408E and G411V) previously shown to have reduced or no transport activity, but correct targeting to the membrane. The mutant UapA constructs expressed well as GFP fusions in Saccharomyces cerevisiae and exhibited similar fluorescent size exclusion chromatography (FSEC) profiles to the wild-type protein, following solubilization in 1% DDM, LDAO or OM + 1 mM xanthine. In order to assess the relative stabilities of the mutants, solubilized fractions prepared in 1% DDM + 1 mM xanthine were heated at 45°C for 10 min prior to FSEC. The Q408E and G411V mutants gave markedly better profiles than either wild-type or the other mutants. Further FSEC analysis following solubilization of the mutants in 1% NG ± xanthine confirmed that G411V is more stable than the other mutants, but showed that Q408E is unstable under these conditions. G411V and an N-terminally truncated construct G411VΔ1-11 were submitted to large-scale expression and purification. Long-term stability analysis revealed that G411VΔ1-11 was the most stable construct and the most suited to downstream structural studies.
Molecular Membrane Biology 06/2012; · 2.86 Impact Factor
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ABSTRACT: The Toll/interleukin (IL)-1 receptor (TIR) domain is an essential component of eukaryotic innate immune signalling pathways. Interaction between TIR domains present in Toll-like receptors and associated adaptors initiates and propagates an immune signalling cascade. Proteins containing TIR domains have also been discovered in bacteria. Studies have subsequently shown that these proteins are able to modulate mammalian immune signalling pathways dependent on TIR interactions and that this may represent an evasion strategy for bacterial pathogens. Here, we investigate a TIR domain protein from the highly virulent bacterium Yersinia pestis, the causative agent of plague. When overexpressed in vitro this protein is able to downregulate IL-1β- and LPS-dependent signalling to NFκB and to interact with the TIR adaptor protein MyD88. This interaction is dependent on a single proline residue. However, a Y. pestis knockout mutant lacking the TIR domain protein was not attenuated in virulence in a mouse model of bubonic plague. Minor alterations in the host cytokine response to the mutant were indicated, suggesting a potential subtle role in pathogenesis. The Y. pestis mutant also showed increased auto-aggregation and reduced survival in high-salinity conditions, phenotypes which may contribute to pathogenesis or survival.
Microbiology 03/2012; 158(Pt 6):1593-606. · 3.06 Impact Factor
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ABSTRACT: Functional characterization of G protein-coupled receptors is essential to ascertain the suitability of a protein target for downstream studies and to help develop optimal expression and isolation procedures. Radioligand binding analysis is a well-established technique, which allows direct measurement of the amount of functional receptor in a sample. It can be readily applied to both membrane-bound and soluble receptor samples and is an ideal method for monitoring the amount of functional protein at each stage in the expression and isolation process. This unit presents protocols for the radioligand binding analysis of the human adenosine A(2a) receptor and provides examples of how these assays can be used at several stages to help optimize expression, solubilization, and isolation procedures.
Current protocols in protein science / editorial board, John E. Coligan ... [et al.] 02/2012; Chapter 29:Unit 29.3.
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ABSTRACT: The isolation of membrane proteins with the aim of producing highly pure, homogeneous, stable, and functional material remains challenging, and it is often necessary to develop protein-specific purification protocols by trial and error. One key tool that is required in the development of a suitable protocol is a functional assay. This unit describes a range of different protocols for isolation of the human adenosine A2a receptor (A(2a)R). These protocols show the importance of developing a robust method for comparing the quality of protein obtained by a combination of biophysical analyses including SDS-PAGE, analytical size-exclusion chromatography, and functional analysis. One of the keys to isolating and maintaining a functional receptor, found not only in the optimal protocol described here but in other published examples, is that there should be no more than two chromatographic steps.
Current protocols in protein science / editorial board, John E. Coligan ... [et al.] 02/2012; Chapter 29:Unit 29.4.
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ABSTRACT: One of the major advantages of using Pichia pastoris is that it is readily adapted to large-scale culture in bioreactors. Bioreactors allow precise regulation of cell growth parameters increasing both yields and reproducibility of the culture. P. pastoris cultures grow to very high cell densities which helps minimise culture volume and facilitates downstream processing of the sample. Here, we provide protocols for the large-scale production of the human adenosine A(2A) receptor (A(2A)R) and provide some details of how bioreactor cultures can be used for optimisation of expression of the human dopamine D2 receptor (D2DR).
Methods in molecular biology (Clifton, N.J.) 01/2012; 866:197-207.
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ABSTRACT: Pichia pastoris is an established host for the production of a wide range of recombinant proteins including membrane proteins. The system has a particularly good track record for the production of G protein-coupled receptors (GPCRs). Generation and screening of expression clones with this system use standard molecular biology techniques. Multiple clones can be generated and screened in a matter of a few weeks making this similar to Escherichia coli in terms of speed. In addition, basic buffer components and the lack of expensive equipment make small-scale expression screening in P. pastoris very cost-effective. Here we describe the procedures used for small-scale GPCR production screening.
Methods in molecular biology (Clifton, N.J.) 01/2012; 866:65-73.
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ABSTRACT: When planning any heterologous expression experiment, the very first critical step is related to the design of the overall strategy, hence to the selection of the most adapted expression vector. The very flexible Pichia pastoris system offers a broad range of possibilities for the production of secreted, endogenous or membrane proteins thanks to a combination of various plasmid backbones, selection markers, promoters and fusion sequences introduced into dedicated host strains. The present chapter provides some guidelines on the choice of expression vectors and expression strategies. It also brings the reader a complete toolbox from which plasmids and fusion sequences can be picked and assembled to set up appropriate expression vectors. Finally, it provides standard starting protocols for the preparation of the selected plasmids and their use for host strain transformation.
Methods in molecular biology (Clifton, N.J.) 01/2012; 866:25-40.
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ABSTRACT: Recent research has highlighted the presence of Toll/Interleukin 1 receptor (TIR)-domain proteins (Tdps) in a range of bacteria, suggested to form interactions with the human adaptor protein MyD88 and inhibit intracellular signaling from Toll-like receptors (TLRs). A Tdp has been identified in Yersinia pestis (YpTdp), a highly pathogenic bacterium responsible for plague. Expression of a number of YpTIR constructs of differing lengths (YpTIR1, S130-A285; YpTIR2, I137-I273; YpTIR3, I137-246; YpTIR4, D107-S281) as fusions with an N-terminal GB1 tag (the B1 immunoglobulin domain of Streptococcal protein G) yielded high levels of soluble protein. Subsequent purification yielded 4-6 mg/L pure, folded protein. Thrombin cleavage allowed separation of the GB1 tag from YpTIR4 resulting in folded protein after cleavage. Nuclear magnetic resonance spectroscopy, size exclusion chromatography, SDS-PAGE analysis and static light scattering all indicate that the YpTIR forms dimers. Generation of a double Cys-less mutant resulted in an unstable protein containing mainly monomers indicating the importance of disulphide bonds in dimer formation. In addition, the YpTIR constructs have been shown to interact with the human adaptor protein MyD88 using 2D NMR and GST pull down. YpTIR is an excellent candidate for further study of the mechanism of action of pathogenic bacterial Tdps.
Microbial Pathogenesis 09/2011; 51(3):89-95. · 1.94 Impact Factor
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Yo Sonoda,
Simon Newstead,
Nien-Jen Hu,
Yilmaz Alguel,
Emmanuel Nji,
Konstantinos Beis,
Shoko Yashiro,
Chiara Lee,
James Leung,
Alexander D Cameron, Bernadette Byrne,
So Iwata,
David Drew
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ABSTRACT: Obtaining well-ordered crystals is a major hurdle to X-ray structure determination of membrane proteins. To facilitate crystal optimization, we investigated the detergent stability of 24 eukaryotic and prokaryotic membrane proteins, predominantly transporters, using a fluorescent-based unfolding assay. We have benchmarked the stability required for crystallization in small micelle detergents, as they are statistically more likely to lead to high-resolution structures. Using this information, we have been able to obtain well-diffracting crystals for a number of sodium and proton-dependent transporters. By including in the analysis seven membrane proteins for which structures are already known, AmtB, GlpG, Mhp1, GlpT, EmrD, NhaA, and LacY, it was further possible to demonstrate an overall trend between protein stability and structural resolution. We suggest that by monitoring membrane protein stability with reference to the benchmarks described here, greater efforts can be placed on constructs and conditions more likely to yield high-resolution structures.
Structure 01/2011; 19(1):17-25. · 6.35 Impact Factor
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Pil Seok Chae,
Kamil Gotfryd,
Jennifer Pacyna,
Larry J W Miercke,
Søren G F Rasmussen,
Rebecca A Robbins,
Rohini R Rana,
Claus J Loland,
Brian Kobilka,
Robert Stroud, Bernadette Byrne,
Ulrik Gether,
Samuel H Gellman
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ABSTRACT: We describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. Members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles.
Journal of the American Chemical Society 11/2010; 132(47):16750-2. · 9.91 Impact Factor
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Pil Seok Chae,
Søren G F Rasmussen,
Rohini R Rana,
Kamil Gotfryd,
Richa Chandra,
Michael A Goren,
Andrew C Kruse,
Shailika Nurva,
Claus J Loland,
Yves Pierre,
David Drew,
Jean-Luc Popot,
Daniel Picot,
Brian G Fox,
Lan Guan,
Ulrik Gether, Bernadette Byrne,
Brian Kobilka,
Samuel H Gellman
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ABSTRACT: The understanding of integral membrane protein (IMP) structure and function is hampered by the difficulty of handling these proteins. Aqueous solubilization, necessary for many types of biophysical analysis, generally requires a detergent to shield the large lipophilic surfaces of native IMPs. Many proteins remain difficult to study owing to a lack of suitable detergents. We introduce a class of amphiphiles, each built around a central quaternary carbon atom derived from neopentyl glycol, with hydrophilic groups derived from maltose. Representatives of this maltose-neopentyl glycol (MNG) amphiphile family show favorable behavior relative to conventional detergents, as manifested in multiple membrane protein systems, leading to enhanced structural stability and successful crystallization. MNG amphiphiles are promising tools for membrane protein science because of the ease with which they may be prepared and the facility with which their structures may be varied.
Nature Methods 10/2010; 7(12):1003-8. · 19.28 Impact Factor
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ABSTRACT: Recent high resolution structures of modified G-protein coupled receptors (GPCRs) have provided major insight into the mechanisms of receptor-ligand binding. However understanding of the complete mechanism of GPCR function remains limited. This study characterised C-terminally truncated versions of the human adenosine A(2A) receptor (A(2A)R) with a view to producing protein suitable for structural studies. The constructs terminated at residue A316, removing the intracellular C-terminal tail, or V334, producing a C-terminal tail equivalent in length to that of rhodopsin. Higher levels of functional receptor before and after solubilisation were obtained for both C-terminally truncated constructs compared to the wild-type receptor (WT) as assessed by radioligand binding analysis using [(3)H]ZM241385. The construct which yielded the highest level of functional receptor, V334 A(2A)R, was purified in DDM to high homogeneity with a final yield of 2 mg/L. Binding analysis revealed that the purified receptor had a specific activity of 20.2+/-1.2 nmol/mg, close to the theoretical maximum. Pure V334 A(2A)R was resistant to degradation over 15 days when stored at 4 degrees C or 20 degrees C and showed remarkable functional stability when stored at 4 degrees C, retaining 84% of initial functionality after 30 days. This construct is an excellent candidate for structural studies.
Protein Expression and Purification 05/2010; 74(1):80-7. · 1.59 Impact Factor
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ABSTRACT: The last five years have seen a dramatic increase in the number of membrane protein structures. The vast majority of these 191 unique structures are of membrane proteins from prokaryotic sources. Whilst these have provided unprecedented insight into the mechanism of action of these important molecules our understanding of many clinically important eukaryotic membrane proteins remains limited by a lack of high resolution structural data. It is clear that novel approaches are required to facilitate the structural characterization of eukaryotic membrane proteins. Here we review some of the techniques developed recently which are having a major impact on the way in which structural studies of eukaryotic membrane proteins are being approached. Several different high throughput approaches have been designed to identify membrane proteins most suitable for structural studies. One approach is to screen large numbers of related or non-related membrane proteins using GFP fusion proteins. An alternative involves generating large numbers of mutants of a single protein with a view to obtaining a fully functional but highly stable membrane protein. These, and other novel techniques that aim to facilitate the production of protein likely to yield well-diffracting crystals are described.
Current Protein and Peptide Science 03/2010; 11(2):156-65. · 2.89 Impact Factor
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ABSTRACT: The Nucleobase-Ascorbate Transporters (NATs) family includes carriers with fundamental functions in uptake of key cellular metabolites, such as uric acid or vitamin C. The best studied example of a NAT transporter is the uric acid-xanthine permease (UapA) from the model ascomycete Aspergillus nidulans. Detailed genetic and biochemical analyses have revealed much about the mechanism of action of this protein; however, the difficulties associated with handling eukaryotic membrane proteins have limited efforts to elucidate the precise structure-function relationships of UapA by structural analysis. In this manuscript, we describe the heterologous overexpression of functional UapA as a fusion with GFP in different strains of Saccharomyces cerevisiae. The UapA-GFP construct expressed to 2.3 mg/L in a pep4Delta deletion strain lacking a key vacuolar endopeptidase and 3.8 mg/L in an npi1-1 mutant strain with defective Rsp5 ubiquitin ligase activity. Epifluorescence microscopy revealed that the UapA-GFP was predominately localized to the plasma membrane in both strains, although a higher intensity of fluorescence was observed for the npi1-1 mutant strain plasma membrane. In agreement with these observations, the npi1-1 mutant strain demonstrated a approximately 5-fold increase in uptake of [(3)H]-xanthine compared to the pep4Delta deletion strain. Despite yielding the best results for functional expression, in-gel fluorescence of the UapA-GFP expressed in the npi1-1 mutant strain revealed that the protein was subject to significant proteolytic degradation. Large scale expression of the protein using the pep4Delta deletion strain followed by purification produced mg quantities of pure, monodispersed protein suitable for further structural and functional studies. In addition, this work has generated a yeast cell based system for performing reverse genetics and other targeted approaches, in order to further understand the mechanism of action of this important model protein.
Protein Expression and Purification 02/2010; 72(1):139-46. · 1.59 Impact Factor
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ABSTRACT: Tripartite efflux systems are responsible for the export of toxins across both the inner and outer membranes of gram negative bacteria. Previous work has indicated that EmrAB-TolC from Escherichia coli is such a tripartite system, comprised of EmrB an MFS transporter, EmrA, a membrane fusion protein and TolC, an outer membrane channel. The whole complex is predicted to form a continuous channel allowing direct export from the cytoplasm to the exterior of the cell. Little is known, however, about the interactions between the individual components of this system. Reconstitution of EmrA+EmrB resulted in co-elution of the two proteins from a gel filtration column indicating formation of the EmrAB complex. Electron microscopic single particle analysis of the reconstituted EmrAB complex revealed the presence of particles approximately 240x140A, likely to correspond to two EmrAB dimers in a back-to-back arrangement, suggesting the dimeric EmrAB form is the physiological state contrasting with the trimeric arrangement of the AcrAB-TolC system.
Biochemical and Biophysical Research Communications 02/2009; 380(2):338-42. · 2.48 Impact Factor
